Method of producing colloid relief images

ABSTRACT

IN A PROCESS FOR PRODUCING A COLLOID RELIEF IMAGE BY EXPOSING A LIGHT SENSITVE COLLOID LAYER TO THE ACTION OF LIGHT TO PRODUCE A DIFFERENTIALLY HARDENED COLLOID LAYER CONTAINING HARDENED PORTIONS WHICH HAVE BEEN EXPOSED TO LIGHT AND UNHARDENED PORTIONS, THE IMPROVEMENT WHICH COMPRISES REMOVING THE UNHARDENED PORTIONS BY CONTACTING THE DIFFERENTIALLY HARDENED COLLOID LAYER WITH A HOT AQUEOUS SALT SOLUTION, E.G., A CONCENTRATED SODIUM CHLORIDE SOLUTION, TO SOFTEN THE UNHARDENED PORTIONS, FOLLOWED BY TREATMENT OF THE DIFFERENTIALLY HARDENED COLLOID LAYER WITH COLD WATER TO REMOVE THE SOFTENED UNHARDENED PORTIONS OF THE COLLOID LAYER ESSENTIALLY AS PARTICLES SUSPENDED IN THE WATER, AND PERMITTING REUSE OF BOTH THE HOT SALT SOLUTION AND THE COLD WATER, FOLLOWING REMOVAL OF THE SUSPENDED PARTICLES, FOR FURTHER PROCESSING TO PROVIDE COLLOID RELIEF IMAGES AS ABOVE DESCRIBED.

United States Patent @lfice Patented Oct. 17, 1972 Int. Cl. G03c 5/00 US. Cl. 96-35 13 Claims ABSTRACT OF THE DISCLOSURE In a process for producing a colloid relief image by exposing a light sensitive colloid layer to the action of light to produce a differentially hardened colloid layer containing hardened portions which have been exposed to light and unhardened portions, the improvement which comprises removing the unhardened portions by contacting the differentially hardened colloid layer with a hot aqueous salt solution, e.g., a concentrated sodium chloride solution, to soften the unhardened portions, followed by treatment of the differentially hardened colloid layer with cold water to remove the softened unhardened portions of the colloid layer essentially as particles suspended in the water, and permitting reuse of both the hot salt solution and the cold water, following removal of the suspended particles, for further processing to provide colloid relief images as above described.

The present invention relates to a method for the economical production of colloid relief images, and is particularly concerned with improvement in procedure for removing the unhardened portions of a differentially hardened colloid relief layer following exposure of the light sensitive colloid layer to light, employing treating solutions under conditions which permit of the facile re-use or recycling of the treatment solutions for further processing of colloid relief images, thereby avoiding the necessity of the employment of large volumes of water, and also minimizing sewage or pollution problems presented by conventional treating solutions containing substantial amounts of dissolved colloids.

Colloid relief images are produced by washing out the unhardened portions from a locally differentially tanned or hardened colloid layer. The differential hardening is effected, as is also well known, by various means under the influence of light, which produces a hardening action in gelatin, gum, or synthetic colloids, through the action of the light on sensitizers such as bichromate salts, diazo compounds, azides and iron salts and numerous other substances proposed in the literature, which are present in the colloid layer. The tanning or hardening can be performed also indirectly from exposed silver salts by the aid of tanning development or by interaction with chromate salts or iron salts, as well known in the art.

In the conventional processes of the prior art, after the local differential hardening or tanning of the colloid layer is effected, the unhardened gelatin, whether colored or uncolored, is washed out in warm water. Thus, the relief image is developed irrespective of the subsequent utilization of the relief image, that is, whether it is left in situ or transferred. The formation of the relief image following exposure to light, consists of washing out the unhardened portion of the image with water of elevated temperature which softens up and dissolves the unhardened portion. The hardened portions as a rule are then treated with cold water to set the relief image or to make it more firm.

The above prior art procedure presents considerable problems and substantial expense in requiring in the first place substantial quantities of warm water of controlled temperature for removing the unhardened colloid portions of the exposed differentially sensitized colloid layer, and further, presents the problem of disposing of relatively large quantities of water containing dissolved colloids and which is not suited for other purposes.

These problems are particularly acute in connection with the large scale production of color proofing materials for graphic art purposes or the production of relief images for color photographic, still or motion picture purposes.

The present invention, as distinguished from conventional prior art processes renders the production for development of relief images much more economical and avoiding the above noted problems of the conventional procedures for this purpose. Thus, according to the present invention, the production of relief images, colored or uncolored, can be performed with greater convenience on a large scale, and the invention procedure is more controllable and economical than prior procedures.

The present invention comprises an improved method which makes more economical the development of a differentially hardened colloid layer, by a two step procedure comprising treatment with a first aqueous solution at elevated temperature followed by treatment with a second cold water bath. The features of the invention method include the supply of a bath of controlled elevated temperature which can be re-used several times for treating the unhardened portions of the colloid layer, and which can be kept free, or relatively free, of the debris of the unhardened portions of the colloid layer, and which can be conveniently filtered, if necessary, and re-circulated, and the supply of a cold bath following treatment with the hot aqueous solution to complete the development in the manner set forth in detail below.

According to the invention, a differentially hardened c olloid layer on a support, e.g., produced by the action of light on a colloid layer containing a light sensitive substance, which provides a hardened or tanned image portion by the direct action of light, with remaining unhardened portions, is treated to remove the unhardened portrons substantially without dissolving the hardened portion, to form a colloid relief image, by contacting such differentially hardened layer with an aqueous salt solut on at elevated temperature and at a concentration sufficient to soften the unhardened portions substantially Without removal of such softened unhardened portions, followed by contacting such differentially hardened colloid layer with water at temperature ranging from ambient to cold, to remove such softened unhardened portions of thet COllOld layer essentially as particles suspended in such wa er.

The elevated temperature bath or the hot water bath employed in the first step of the invention process contains a substantial amount of a salt which functions to essentially soften the unhardened portions of the differentially hardened colloid layer, but preventing such softened portions from disintegrating and entering the solution, or if so, only to a very limited degree and in a precipitated and generally filterable form. For this purpose a warm to hot solution of a neutral, or weakly acid, or weakly alkaline salt is employed. Examples of salts which can be employed in such solutions are the alkali chlorides, such as sodium or potassium chloride; sodium, potassium, magnesium, or ammonium sulphate; alkali phosphates, such as trisodium or tripotassium phosphate, disodium or dipotassium phosphate; or mixtures of such salts can be employed, such as a mixture of disodium hydrogen phosphate and trisodium phosphate. The salts employed are those which have substantial solubility in water.

The concentration of the salt solution can vary to a considerable degree for the softening of the unhardened or less hardened portions of the differentially hardened colloid layer. Salt concentration is controlled so that the unhardened colloid does not disintegrate and pass into the salt solution, except perhaps in trace amounts, and under the latter conditions, is in suspended form rather than in solution. Thus, for example, concentration of the salt solution can range from saturated salt solutions down to about 0.1 saturated, depending upon the nature of the colloid and of the particular salt solution.

Temperature of the salt solution can vary widely for treatment according to the invention, and is usually in the range of about 35 to about 100 C. Time of treatment with the salt solution can range from about 1 to about minutes, but such range is of course not critical.

The salt solution can also contain, in addition to the above noted salt, an organic solvent, e.g., glycerin, glycol, and the like, or substances such as urea, which assist the salt in softening the unhardened portions of the colloid layer substantially without causing any unhardened portion to enter the solution to any substantial extent.

The salt solution also can contain inorganic or organic hardeners or tanning agents such as potassium-alum, chrome-alum, formaldehyde, dialdehydes such as glyoxal, succinic aldehyde, glutaraldehyde, 2-hydroxy adip-aldehyde, or any other hardening or tanning agent known in the art may be added in order to control the melting or softening point of the colloid for the intended processing temperature at which the salt solution may be used. The quantity or nature of these additional substances depends on the nature of the colloid, its melting point and salt sensitivity.

The unexposed portions of the so-treated layer are thus softened without developing a visible relief image. The degree of softening is controlled by the amount and time of light exposure and also by the time and temperature of the treatment with the salt solution. The exact time and temperature can be determined by a preliminary test, but as noted above, temperature of the salt solution and time of treatment therewith are not critical and can be varied to a considerable degree.

Following treatment with the warm or hot salt solution, the differentially hardened colloid layer now having softened unhardened colloid portions, is treated with room temperature water or cold water, e.g., ranging from about 3 to about 25 C., to remove such softened unhardened portions of the colloid, thus completing the development of the relief image. Such ambient temperature or cold water bath causes removal or disintegration of the softened unhardened colloid portions, so that following such ambient or cold water treatment, the colloid particles thus removed chiefly are in suspended form in the bath, without going into solution in the bath, or forming very fine dispersions therein, so that such suspended particles can be readily removed from the bath by filtration or settling from the cold water, thus permitting the re-use of the water and substantially reducing or eliminating contamination or pollution of the cold water. Time of treatment with such ambient temperature or cold water is generally relatively short, particularly where a water spray or jet is used, until the softened colloid is completely washed out. The time of such treatment can range from about /2 to about 10 minutes.

The differentially hardened colloid layer can be treated in the elevated temperature salt solution and in the ambient temperature or cold water solution in any suitable manner, as for example, by employment of stationary baths, or by continuous flow of these treating liquids as in spray form, in contact with the differentially hardened colloid layer. Both the salt solution and cold water solution, following removal of debris therefrom as by filtration, can be re-used in the process. Thus, the invention process renders the processing or development of exposed colloid layers more economical and more controllable, and avoids the use of large quantities of controlled temperature hot water for removing and dissolving unhardened portions of the colloid layer, and avoiding the necessity of sewering such solutions containing dissolved colloids.

Various hydrophilic hardenable colloids can be employed in the light sensitive colloid layer used to produce colloid relief images, employing the invention principles for removing the unhardened portions of the exposed light sensitive colloid layer. Examples of such colloids are polyvinyl alcohol, polyacrylamide or polymeric isopropyl acrylamide, methyl cellulose, sodium carboxymethyl cellulose, natural gums such as gum arabic, guar gum, agar agar, and the like. If desired, mixtures of such colloids can be employed, such as a mixture of gelatin and 25 to 50% low viscosity polyvinyl alocohol.

The support or substrate to which the hardenable colloid containing the light sensitive substance, e.g., light sensitive azide, or light sensitive bichromate, can be applied, can be opaque or transparent, for example, paper, a plate, or plastic, e.g., transparent film, such as cellulose acetate, polyester or polystyrene film, and the like.

The following are examples of practice of the invention:

EXAMPLE 1 A light sensitive material is provided consisting of a gelatin layer which contains a light sensitive aromatic azide, and a coloring substance in the form of an immobile dye, coated on a transparent subbed polyester film base.

Such gelatin layer contains between 0.3 to 1 gram gelatin per square meter and has distributed therein a dye in a quantity of 0.25 to 0.5 gram per square meter of coated base. This dye is a magenta dye, prepared by coupling diazotized anhydro-para-(m-amino-benzene sulphamino-) benzyl alcohol, a polymeric compound, with 2-hydroxy-naphthalene-3,6-disulphonic acid, or a yellow polymeric dye produced by coupling the same polymeric diazo compound with 1 (p sulphophenyl)-3-methyl pyrazolene-(S), in known manner. This layer further contains 0.25 to 0.5 gram 4,4'-diazido stilbene-2,2-disulfonate disodium salt per square meter. This is a light sensitive compound which upon exposure to light hardens the gelatin.

The colored gelatin layer described above is exposed through the transparent base under a half tone negative by exposure at a distance of 2 feet, under a 275-watt sunlamp for about 3 to 5 minutes. The exposed gelatin coating is then immersed in a saturated solution of sodium chloride having a temperature between 40 and 50 C. The colloid layer is maintained in the hot salt solution between 1 to 5 minutes. The so treated layer is thus softened without developing a visible relief image.

After the colloid layer is removed from the salt solution it is rinsed in stationary or running cold water at a temperature of about 17 C. for about 1 to about 5 minutes. For this purpose it is advantageous to apply the cold water from a spray or from a wedge-shaped nozzle. This treatment removes the unhardened and softened gelatin, and such removed gelatin is present in the cold water in the form of particles suspended in the water. A relief image with clear whites and good definition is thus produced.

The above hot salt solution and the cold water solution, following removal of suspended particles of gelatin from the latter solution, are re-used for further processing and development of exposed gelatin layers, as described above, to produce relief images.

EXAMPLE 2 The procedure of Example 1 is followed, except that in place of the saturated sodium chloride solution utilized in treatment of the exposed gelatin coating, there is employed respectively (a) a saturated solution of sodium sulfate, (-1)) a saturated solution of ammonium sulfate, (0) a saturated solution of trisodium phosphate, and (d) a saturated solution of a mixture of equal proportions of disodium hydro;

gen phosphate and trisodium phosphate, such salt solutions each being employed at temperature of about 50-60" C., to soften the unhardened portions of the gelatin layer without developing the relief image.

Results similar to those of Example 1 are obtained.

EXAMPLE 3 The procedure of Examples 1 and 2 is repeated except that the respective salt solutions have a concentration of about 0.5 saturated.

Results simliar to those in Examples 1 and 2 are obtained, the resulting salt solutions following a period of treatment, however, containing a trace or very small amounts of suspended gelatin particles, which are filtered from such solutions, and such salt solutions reused.

EXAMPLE 4 The procedure of Example 1 is repeated except that there is also added to the sodium chloride salt solution used for treatment of the exposed gelatin solution, about 1 to 5% glycol as a futrher aid in softening the unhardened gelatin portions.

EXAMPLE 5 The procedure of Example 1 is repeated except that there is also added to the sodium chloride solution used for treatment of the exposed gelatin, .01-05% of potassiumalum. or 0.050.1% glyoxal, and the resulting solution is employed at temperature of about 70-75 C.

Results similar to those of Example 1 are obtained.

Instead of utilizing water soluble dyes for coloring the colloid, the colloid material can contain suspended dyes or pigments which are incorporated by grinding such dyes or pigments and dispersing them in the gelatin solution or other hardenable colloid. Such dyes are, for example, phthalocyanine blue; 01. pigment blue Cl. pigment yellow #1, and the like. The thickness of the gelatin layer may vary from 2-10 microns, and the quantity of the dye or pigment can vary between .01 to 1 gram per square meter.

In lieu of an azide sensitizer, diazo sensitizers such as diazotized 3,3'-diamino-4,4'-dihydroxy-5,5'-dicarboxy diphenyl methane or other diazo sensitizers which produce tanned diazo images, can be used in the colloid layer. The above pigment-containing colloid layers may contain sensitizers such as potassium or ammonium bichromate which are incorporated by bathing and subsequent drying of these pigmented materials as known in the art. After exposure, these materials are treated according to the invention procedure.

The coloring matters or pigments may also be incorporated in silver halide emulsions, and the silver halide emulsion, after exposure, is treated in a well-known way by tanning development, or the silver image is developed in the usual way and subsequently treated with a tanning bleach, and dissolution of the unhardened colloid portion is effected in the same manner as described above; that is, the differentially hardened colloid layer is softened first by treatment with a warm or hot salt solution, followed by dissolution of the unhardened portions, e.g., with a spray of cold water, according to the invention.

The relief images can be colorless and dyed subsequently with transferable or non-transferable dyes in a known manner, for the production of dye transfer images.

The folllowing are additional examples of the invention process:

EXAMPLE 6 A gelatin layer containing 0.5 gram of CI. pigment blue per square meter of coating, and also containing a diazo sensitizer such as diazotized 3,3'-diamino-4,4'-dihydroxy 5,5'-dicarboxy-diphenylmethane, is coated on a transparent base in a quantity of about 1.0 gram per square meter. This sensitized layer is exposed under a half tone negative through the base with an 18 ampere are light for five minutes at a distance of 1 meter.

The exposed material is immersed in a concentrated solution of either sodium chloride, sodium sulfate, magnesium sulfate or ammonium sulfate, at 55 C. for about 3 minutes. The layer which contains a tanned image is softened but remains substantially undissolved upon such treatment. The layer is thereafter rinsed in cold water as described in Example 1, and a tanned relief image is thus produced.

EXAMPLE 7 In the above described gelatin layer of Example 6, the sensitizer therein is replaced by an inorganic sensitizer in the form of potassium or ammonium bichromate, employing about 0.2O.5 gram per square meter of coating. Such bichromate sensitizer is introduced in the gelatin layer in a manner well known in the art, by bathing the pigmented colloid layer in a 4% solution of the bichromate for 5 minutes and subsequent drying in the absence of light.

The layer is exposed and developed in a manner similar to that described above in Example 6.

EXAMPLE 8 This example illustrates incorporation of the coloring matter or pigment into a silver halide emulsion.

The soluble polymeric dyes described in Example 1, are respectively incorporated into a gelatin layer containing about 1.5 grams silver bromide per square meter of coating. Such layer is exposed in a camera or in a printing frame in the usual manner and developed for 2 to 4 minutes in a freshly mixed tanning developer, containing 1 gram pyrocatechol and 1 gram potassium carbonate per liter of water, followed by rinsing briefly with cold water.

The resulting tanned layer is introduced into a saturated sodium chloride solution at 50 C. and maintained in such solution for 3 to 5 minutes. The layer is then rinsed with cold water as described in Example 1, producing a tanned relief image.

EXAMPLE 9 The exposed material of the previous Example 8 is developed in a non-tanning developer, namely, D.K. 50, which is a wellknown commercially available metol-hydroquinone developer. After washing in cold water, the developed layer is treated with a bleach hardener for 1 minute, composed of 2% ammonium or potassium bichromate and 1 to 3% hydrochloric acid.

After rinsing in cold water, the so treated material is immersed for 3 minutes in a 0.5 saturated sodium chloride solution, at 50 C. for 3-5 minutes, and is then developed by treatment in cold water as described in Example 1, to produce a relief image.

Although various modifications of my invention have been described for purposes of illustration, the invention is not to be taken as limited except by the scope of the appended claims.

I claim:

1. In a process for producing a colloid relief image by removing the unhardened portions from a differentially hardened hydrophilic colloid layer produced by the action of light on a colloid layer containing a light sensitive substance selected from the group consisting of bichromate salts, diazo compounds, azides, iron salts and silver salts, which provides a hardened or tanned image portion with remaining unhardened portions, the improvement which comprises contacting said differentially hardened colloid layer with an aqueous salt solution consisting essentially of a salt selected from the group consisting of soluble sulfates, chlorides and alkali metal phosphates, at temperature between about 35 and about C. and at a concentration ranging from saturated down to about 0.1 saturated to soften the unhardened portions substantially without removal of said softened portions, softening said unhardened portions, and contacting said differentially hardened colloid layer with Water at temperature ranging from about 3 to about 25 C., to remove said softened unhardened portions without dissolving said unhardened colloid portions, said unhardened colloid portions being present essentially as particles in suspension in said water.

2. In a process as defined in claim 1, said salt solution containing an organic solvent or urea to further assist in softening said unhardened portions of said colloid.

3. In a process as defined in claim 1, wherein said salt is selected from the group consisting of sodium and potassium chloride, sodium, potassium, magnesium and ammonium sulphate, trisodium and tripotassium phosphate, and disodiurn and dipotassium phosphate, and mixtures of said salts.

4. In a process as defined in claim 1, said period of treatment in said salt solution being carried out for a period ranging from about 1 to about 15 minutes, and the period of treatment in said water ranging from about /2 to about minutes.

5. In a process as defined in claim 1, said salt in said salt solution being sodium chloride and said treatment with said salt solution being carried out for a period ranging from 1 to about minutes.

6. In a process as defined in claim 1, the colloid of said layer being gelatin.

7. In a process as defined in claim 5, the colloid of said colloid layer being gelatin.

8. In a process as defined in claim 1, said colloid of said colloid layer being gelatin, said colloid layer being colored and said light sensitive substance in said colloid layer being a light sensitive aromatic azide.

9. In a process as defined in claim 1, said colloid of 11. In a process as defined in claim 5, said colloid of said colloid layer being gelatin, said gelatin layer being colored with a pigment and said light sensitive substance being a light sensitive aromatic azide.

12. In a process as defined in claim 5 said colloid of said colloid layer being gelatin, said light sensitive substance being a light sensitive silver halide, and including treating said exposed silver halide emulsion in a tanning developer to form said differentially hardened colloid 1a er.

13. In a process as defined in claim 5, said colloid of said colloid layer being gelatin and said light sensitive substance being a light sensitive bichromate.

References Cited UNITED STATES PATENTS 1,609,091 11/1926 Miller 96-35 1,634,658 7/1927 Flammer 9635 2,047,124 7/1936 Cutts 9635 3,169,066 2/1965 Hoerner 96-35 3,275,438 9/1966 Levin 9635 3,295,974 1/ 1967 Erdmann 96-35 1,923,764 8/1933 Troland 96-35 2,257,105 9/1941 Champion 96-35 2,494,068 1/1950 Speck 9660 FOREIGN PATENTS 548,672 10/1942 Great Britain 96-35 581,479 10/ 1946 Great Britain 96-35 NORMAN G. TORCHIN, Primary Examiner I. R. HIGHTOWER, Assistant Examiner U.S. Cl. X.R. 96--35, 49 

